I'm working on the traditional vibration issue of the X-frame caddy. This is a Coupe deville from -59, and she vibrates at 50-60mph. Theres no issues at lower or higher speeds. I tried to search all the old topics about this issue, but I didn't find any clear solution or recommended angles for this two piece propeller shaft?
Short info about the car before any suggestions! This car has been completely refurbished, and I mean 100% parts has been restored/renewed/replaced etc. So the driveshaft itself is rebuilt with new U-joints, and it has been bench tested and balanced. Of course the center support is new with new bearing. Diff is replaced by used original in great condition. Engine & tranny has been completely restored.
So all is there, and all is good and working, but still vibrates. The car has been "ready" for a 7-years now, and I have driven it something like 8000miles. It works nicely except this vibration issue.
During reassembly I tried to use all the original shimming, but seems that I have not installed the ones under the center support. There is 3-piece shims between support arms and body, the engine & tranny mounts are new.
Now I want to try adjust the driveline, but all the different info & lack of clear values frustrates me. I bought a level box and measured the angles. Tranny is approx 5' degrees down, first shaft 2.3' down, second shaft 1.3' down & pinion 0.5' up.
I would like to start from the diff, but not sure about the correct angle? The shop manual says (IMO) that it should be 3', but nothing about the slope, up/down? From reading the older topics I assume it should be nose upwards, but should it be really 3'? I think it would come up when I remove the shims from the support arms, but I'm not sure would it mean that the "driveangle" should be 3', so the diff should be in -1.5' and the rear shaft at the same 1.5', -1,5-1,5=-3'? But then how to adjust the center support and the tranny?
I watched this youtube video, and it seems to be ok, but why he is decreasing the value at the pinion when it is in different slope than the shaft? Shouldn't it be increased?
If I put these values to the Dana calculator, it increases se angle value.
https://youtu.be/f1m-Fh5kiRU
https://spicerparts.com/calculators/driveline-operating-angle-calculator
Is there anyone who could help me with this?
First thing to check is whether all the u joints are in "phase". Even slightly off will cause a vibration. Plenty of pics and info on the internet, about phasing the joints on a 2 piece driveshaft and the suggested pinion angles., with good pictures. I would paste them here but the info is readily available on Google.
Hi Dave,
All joints are in phase and the driveshaft is balanced in machinery shop, where it runs smoothly.
I tried to find info about these two piece shafts, but this Cadillac type seems to be speccsed differently. For starters the engine cannot be aligned to first shaft due the frame design. It is impossible to adjust the angle for recommended 0,5' without hitting the frame. If I would know the correct position of the diff, I would be able to try adjust the center joint to match the rear. The first joint seems to leave 2-3' angle.
If you look at the pictures on line you will see the angle of joints have to be parallel to each other, say 1 degree up , next joint ideally 1 degree down. The pictures are self explanatory.
It seems to me that you need to get the operating angle between the transmission output shaft and front drive shaft section closer to zero. The operating angle now is 2.7 degrees by your measurements. You might need to shim the transmission mount and shim the carrier. Once that is done, you should be able to nose up on the pinion shaft to match the angle of the transmission output shaft.
I suffered the same problem with my '60 CDV, and did everything to try and fix it.
The last thing I tried was to replace the upper ball joint in the 'A' arm over the top of the diff centre.
Mine was totally shot, even though everything else in the suspension and bushing department was good.
It was a simple task to replace, after the arm was removed, and that solved my issue.
Bruce. >:D
Ideally you do not want the angles exactly the same. The front and rear shaft working angles should be parallel, this assumes the frt shaft has a rear joint engaging the rear at the center support. Yes on each shaft the joints are in line, but the angle difference of the 2 shafts must be parallel, good pics on google. Hard to explain, but the pics make it clear.
Calling Eric DeVirgilis, I thought Eric told me the 1959s flutter a bit at about 55-60 MPH. Above and below that nothing.
Maybe Eric will chime in. Maybe my memory fails me. Not sure why they do that.
But it is very slight as I remember no big vibrations, just a slight one.
When I worked for GM, back in the day, I had an 8 year old 59 Coupe, driveline was oe, I don't remember a noticeable vibration attributal to the drive train. As mentioned by Tassie, the ball stud over the diff housing, if worn would alter the pinion angle, most noticeable on acceration.
Thanks for ansvers. All the bushings are new, including the center ball-joint over the differential. I need to check tightness of the bolts/nuts in the chassy. After it I'll try to adjust the angles of the shaft.
Quote from: klinebau on February 02, 2022, 05:04:48 PM
It seems to me that you need to get the operating angle between the transmission output shaft and front drive shaft section closer to zero.
Somewhere I read that an universal joint MUST have some angle otherwise it will self-destruct. When I restored my '57 Brougham, I did not pay attention to the angles; the output shaft at the end of the transmission had an angle of almost 0°. Soon after, I had to replace the joint because of galling. By installing washers under the transmission I could get a decent angle.
The angle has to be there as if there is no angle, the needle rollers will not turn, and will self-destruct because they are not moving, and therefore the minimal mating surface will fail.
If a joint is always inline, then one may as well use a bushing, or spline.
In my Dragster, I used a Greek Coupler to join the transmission output shaft to the Diff Pinion. This is just a short spline coupling and a slip yoke for ease of uncoupling.
Bruce. >:D
I adjusted the rear mount up for 5mm(0.20"), then I removed one shim of the three below the support arms. This way I get first joint angle to 2.7' (between shaft and frame is only 0.25-0.3" room), second joint is now 1.2' and third 1.7'. Now they all are under 3' which is the common guide. The rear joints might be able to get closer to that 1.2' by removing another shim, but I will test this setting first. Too bad that we are in the middle of winter with a meter of snow, so it takes some time to get for a test drive.
I will change some seals to transmission at the same time while the car is already up, so quick question regarding that. I will change the output shaft seal and just noticed that there is play in the outputshaft sidewards, I assume that it always have some play, but how much is ok? Or is there any values for that? Tranny has been refurbished about 8-years ago, there's no issues with it othervice than oil leaks. Mosty the oil comes from the pan seal, which I will change after I ensure that the pan is straight. I'm going to add lasercutted bezel under the screws to avoid screwholes to strech & cause leaking.
Probably one of the more frustrating issues. Hard to detect, hard to fix, and potentially costly(hours) to resolve.
Since everything has been replaced or repaired, that makes it more difficult because the new parts may not be equivalent or installed the same. Something for those that contemplate "complete" restoration to understand.
If the springs were changed/worn, tires, etc may be involved as well. These two piece drive shafts are PIA, but necessary for the length. It's best to mark it when disassembling and put back exactly, but if the frame and/or rearend was involved, that wasn't going to happen.
Somewhat an artifact of the X-frame design. The X is on center where the drive shaft must operate. So you can't have a long drive/propellor shaft moving around in that hole.
All I can suggest is you find a place that specializes rearend/differential repair and let them help work it out. It may end up worse, before it gets better.
I had a similar issue with one of my 4x4s, and the shop was pulling it's hair out, changed parts, nothing fixed. Turned out I had hauled a large load and the springs where extended and did not return to "home. Later, after hauling another load, springs returned and vibration disappeared. Cost me several hundred for nothing.
Technically, it's a dynamic resonance issue when one rpm produces but other do not. Shafts have "frequencies" just like instruments/notes. When the rotation induced vibration matches they "resonate". Harmonic resonance is vibration waves overlapping and the peaks and valleys are synchronized so the amplitude increases. This can destroy bearings very easily. Industrially I dealt with much larger shafts, and it isn't pretty when it happens.
You may have to find out what's causing the resonance, drive alignment is only one facet, as noted above.
The (pinion) angle is to allow the car suspension to move up and down without binding things up. U-joint only have so many degrees of movement. I would suspect, don't know for sure, that info maybe contained in the shop manual of other period mechanics manuals.
Have you seen this thread? https://forums.cadillaclasalleclub.org/index.php?topic=160401.0 (https://forums.cadillaclasalleclub.org/index.php?topic=160401.0)
Really think you ought to be shooting for reducing the working angle between trans output shaft and front-half of driveshaft with the understanding that it can't be or shouldn't be zero. At this point, the back-half of the driveshaft acts as a one-piece so you can angle the pinion shaft to be roughly parallel with trans output shaft angle.
Right now there is nothing to balance out the 2.7 degree working angle it is creating a second order vibration in the driveline.
Quote from: klinebau on February 03, 2022, 02:39:46 PM
Have you seen this thread? https://forums.cadillaclasalleclub.org/index.php?topic=160401.0 (https://forums.cadillaclasalleclub.org/index.php?topic=160401.0)
Really think you ought to be shooting for reducing the working angle between trans output shaft and front-half of driveshaft with the understanding that it can't be or shouldn't be zero. At this point, the back-half of the driveshaft acts as a one-piece so you can angle the pinion shaft to be roughly parallel with trans output shaft angle.
Right now there is nothing to balance out the 2.7 degree working angle it is creating a second order vibration in the driveline.
The tranny-first half angle was over 5-degrees before any adjustment. With the shimming I got it below 3-degrees. I'm willing to see what this will do. It is impossible to raise the tranny anymore, or the shaft will hit the frame. There's no shims under the center support either, so getting the first shaft more lined up with tranny, the center support should be cutted to get it lower and that is something I don't want to do. Maybe if I get another center support, I could chop it and try how it works. I remember, that in my original center support had double fixing nuts. It looked like it could be cutted if needed. The one I got back when buying new does not have such a feature.
On both my '58 an '60 Eldorado Brougham's, there was around 1/16" shim under the center carrier bearing on the prop shaft. When have the prop shafts repaired, I reinstalled using the same shim and don't have an issue. It seems I read somewhere that the shims were added for this kind of issue.
David